Bacterial peptidoglycan in rheumatoid arthritis and multiple sclerosis

The human body is always in close contact with billions of bacteria located at all mucosal sites and prominently in the gut. This bacterial population, commonly referred to as the microflora, is established early following birth, remains constant in a given individual over his or her life span and is of great importance to the host. The bacteria degrade and ferment many of the food components that are not absorbed in the small intestine. Furthermore, the intestinal flora acts as a barrier against food-borne pathogenic bacteria. The mucosal flora also represents a large amount of potent immunostimulatory structures like lipopolysaccharides (LPS) in gram-negative bacteria and peptidoglycan (PG) in both gram-negative and gram-positive bacteria. These structures are important in the resistance to infections but it is cOlrunonly believed that these structures are the major cause of bacterially induced sepsis. It has also been suggested that PG is involved in the persistence of chronic inflammation. In this thesis the role of PG in the pathogenesis of the chronic inflammatory diseases rheumatoid arthritis (RA) and multiple sclerosis (MS) is studied. In this chapter an introduction will be given about PG and its biological activities, and about the pathogenesis ofRA and MS.